1. Field of the Invention
The present invention relates to a preloaded spring mount for a crank pin/rotor bearing assembly of a rotary fluid compressor.
2. Description of Related Art
Rotary fluid compressors of the type used in vehicle air conditioning systems include a crankshaft having a crank pin that is offset for eccentric motion relative to the axis of rotation of the crankshaft. An orbiting ring or scroll rotor is mounted on the crank pin for translational rotary motion in a stator housing to establish moving line contacts therebetween effective to compress a refrigerant gas inducted into the stator housing. Orbiting ring fluid compressors are described in U.S. Pat. Nos. 5,015,161; 5,240,386; 5,284,426; and 5,472,327. An orbiting scroll fluid compressor is described in U.S. Pat. Nos. 4,365,941.
In the design of such compressors, there is provided a small interference fit between the rotor and the bore of the stator housing to provide a radial fluid sealing force at the moving line contacts where the rotor engages the walls of the stator housing. Upon assembly of the compressor components, there is an inherent rotor/stator housing eccentricity that causes the interference fit to be greater than intended in one quadrant and less than intended in the opposite quadrant of rotor motion. This interference fit thereby produces a problem of very high internal stresses in the rotor and other compressor components that may lead to premature fatigue failure of the rotor in service in the compressor.
Certain orbiting ring/scroll fluid compressors for vehicle air conditioning systems include a pressure switch which is used to decouple the compressor clutch if the output pressure of the compressor reaches a set cutoff limit, such as for example, 350 psi. When the vehicle is driven at low speeds, there is insufficient airflow through the air conditioning system condenser to prevent the output pressure from rising to the cutoff limit. As a result, the compressor will cycle between "on" and "off" states in a manner felt by the vehicle driver as an annoying surging of the vehicle motor.
An object of the present invention is to provide a preloaded spring mount for a crank pin/rotor bearing assembly of a rotary fluid compressor for controlling radial fluid sealing force in a manner that overcomes the aforementioned problems associated with rotary fluid compressors used heretofore.